> "guardrails matter" This thing has been solved in the 70s. Basically, have a powerful type system, and a compiler that beats you into submission when you try to stray from the straight and narrow. Languages like (S/OCa)ML, Haskell and Rust will bring this to you. As a consequence, you fight the compiler, and once it submits, you have a good chance it's going to work. The compiler is also the ultimate refactoring tool here. Change the concept? Just change the type in the code and follow through by fixing the error messages the compiler spits out.